Winston Peters' majority in the Northland byelection increased to 4441 votes, according to the official results.
The preliminary results of the March 28 byelection had his winning margin at 4012 votes.
But since the addition of 1579 special declaration votes and overseas votes, his majority has increase by 429 votes.
Mr Peters, the New Zealand First leader, beat National's Mark Osborne and first-time candidate who polled 11, 648 votes.
Labour's Willow-Jean Prime polled 1380 and will not get her $300 deposit back because she did not get at least five per cent of the votes.
Only Mr Peters and Mr Osborne will get refunds on their deposits.
The Electoral Commission said the turnout was 65.4 per cent of the 45,955 voters enrolled.
Of all the votes cast, 30.17 per cent or 13,869 votes were advance votes.
The byelection took place after the resignation of Mike Sabin for undisclosed personal reasons.
The Electoral Commission said it expected to return the writ on April 14 showing the successful candidate, assuming there were no judicial recounts.
However that may be delayed by a few days; the lowest polling candidate, Adam Holland, told the Herald he plans to apply tomorrow for a judicial recount.
The final results:
Adrian Paul Bonner, Independent, 17
Joe Carr, Focus New Zealand, 113
Robin Grieve, Act New Zealand, 68
Herbert Maki, Aotearoa Legalise Cannabis Party, 94
Adam Holland, Independent, 16
Mark, Osborne, National Party, 11, 648
Rob Painting, Climate Party, 39
Winston Peters, 16,089
Rueben Taipari Porter, Mana Movement, 60
Willow-Jean Prime, Labour Party, 1380
Brunce Rogan, Independent, 24